Congenital heart disease monitor

ABSTRACT

A congenital heart disease monitor utilizes a sensor capable of emitting multiple wavelengths of optical radiation into a tissue site and detecting the optical radiation after attenuation by pulsatile blood flowing within the tissue site. A patient monitor is capable of receiving a sensor signal corresponding to the detected optical radiation and calculating at least one physiological parameter in response. The physiological parameter is measured at a baseline site and a comparison site and a difference in these measurements is calculated. A potential congenital heart disease condition in indicated according to the measured physiological parameter at each of the sites or the calculated difference in the measured physiological parameter between the sites or both.

REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No.11/858,053, filed Sep. 19, 2007, entitled “Congenital Heart DiseaseMonitor,” which claims priority benefit under 35 U.S.C. §119(e) fromU.S. Provisional Application No. 60/846,160, filed Sep. 20, 2006,entitled “Congenital Heart Disease Monitor,” which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

Congenital heart disease (CHD) is relatively common, occurring in 5 to10 of every 1,000 live births. Early diagnosis and treatment hasimproved outcomes in this population, but still a number of infants withCHD are sent home undiagnosed. Up to 30% of deaths due to CHD in thefirst year of life are due to such unrecognized cases. Several forms ofCHD are the result of a patent ductus arteriosus (PDA).

FIG. 1 illustrates a fetal heart 102 and a portion of a fetal lung 104.Prior to birth, the lung 104 is non-functional and fluid-filled.Instead, oxygenated blood is supplied to the fetus from gas-exchange inthe placenta with the mother's blood supply. Specifically, oxygenatedblood flows from the placenta, through the umbilical vein 106 and intothe right atrium 122. There, it flows via the foramen 124 into the leftatrium 152, where it is pumped into the left ventricle 150 and then intothe aortic trunk 190. Also, oxygenated blood is pumped from the rightatrium 122 into the right ventricle 120 and directly into the descendingaorta 140 via the main pulmonary artery 180 and the ductus arteriosus130. The purpose of the ductus arteriosus 130 is to shunt blood pumpedby the right ventricle 120 past the constricted pulmonary circulation110 and into the aorta 140. Normally, the ductus arteriosus 130 is onlypatent (open) during fetal life and the first 12 to 24 hours of life interm infants. If the ductus arteriosus remains patent, however, it cancontribute to duct-dependent congenital heart diseases, such as thosedescribed below.

Patent Ductus Arteriosus

FIG. 2 illustrates a neonatal heart 202 with a patent ductus arteriosus230. The ductus arteriosus frequently fails to close in prematureinfants, allowing left-to-right shunting, where oxygenated “red” bloodflows from the aorta 240 to the now unconstricted pulmonary artery 210and recirculates through the lungs 204. A persistent patent ductusarteriosus (PDA) results in pulmonary hyperperfusion and an enlargedright ventricle 220, which leads to a variety of abnormal respiratory,cardiac and genitourinary symptoms.

Persistent Pulmonary Hypertension in Neonates

As shown in FIG. 2, persistent Pulmonary Hypertension in Neonates (PPHN)is a neonatal condition with persistent elevation of pulmonary vascularresistance and pulmonary artery pressure. The pulmonary artery 210 thatnormally feeds oxygen depleted “blue” blood from the right ventricle 220to the lung 204 is constricted. The back pressure from the constrictedpulmonary artery 210 results in a right-to-left shunting of this oxygendepleted blood through the ductus arteriosus 230, causing it to mix withoxygen rich “red” blood flowing through the descending aorta 240.

Aortic Coarctation

Also shown in FIG. 2, coarctation of the aorta is a congenital cardiacanomaly in which obstruction or narrowing occurs in the distal aorticarch 290 or proximal descending aorta 240. It occurs as either anisolated lesion or coexisting with a variety of other congenital cardiacanomalies, such as a PDA. If the constriction is preductal, lower-trunkblood flow is supplied predominantly by the right ventricle 220 via theductus arteriosus 230, and cyanosis, i.e. poorly oxygenated blood, ispresent distal to the coarctation. If the constriction is postductal,blood supply to the lower trunk is supplied via the ascending aorta 240.

SUMMARY OF THE INVENTION

Once a problematic patent ductus arteriosus (PDA) is detected, closurecan be effected medically with indomethacin or ibuprofen or surgicallyby ligation. Clinical symptoms of duct-dependent CHD, however, can varyon an hourly basis, and the required extended and inherentlyintermittent testing is difficult with current diagnostic techniques.These techniques include physical examination, chest x-ray, blood gasanalysis, echocardiogram, or a combination of the above to detect, as anexample, the soft, long, low-frequency murmur associated with a largePDA or, as another example, a retrograde flow into the main pulmonaryartery.

As shown in FIG. 2, a right hand has blood circulating from the leftventricle 250 through the innominate artery 260, which supplies theright subclavian artery (not shown). Because the innominate artery 260is upstream from the ductus arteriosus 230, the oxygen saturation valueand plethysmograph waveform obtained from the right hand are relativelyunaffected by the shunt and serve as a baseline or reference forcomparison with readings from other tissue sites. Alternatively, areference sensor can be placed on a facial site, such as an ear, thenose or the lips. These sites provide arterial oxygen saturation and aplethysmograph for blood circulating from the left ventricle 250 to theinnominate artery 260, which supplies the right common carotid artery(not shown), or to the left common carotid artery 265.

Also shown in FIG. 2, either foot has blood supplied from the descendingaorta 240. A PDA 230 affects both the oxygen saturation and the bloodflow in the descending aorta 240. As stated above, the PDA 230 causesoxygen-depleted blood to be mixed with oxygen-rich blood in thedescending aorta 240. Because the descending aorta 240 supplies blood tothe legs, the oxygen saturation readings at the foot will be loweredaccordingly. That is, duct-dependent CHD may be manifested as a higherarterial oxygen saturation measured at a right hand tissue site(reference) and a lower oxygen saturation measured at a foot tissuesite.

A PDA also allows a transitory left to right flow during systole, whichdistends the main pulmonary artery 280 as the result of the blood flowpressure at one end from the right ventricle and at the other end fromthe aortic arch 290. A left-to-right flow through the shunt 230 into thedistended artery 280 alters the flow in the descending aorta 240 and, asa result, plethysmograph features measured at either foot.Duct-dependent CHD, therefore, may also be manifested as aplethysmograph with a narrow peak and possibly a well-defined dicroticnotch at a hand baseline site and a broadened peak and possibly no notchat a foot site.

Further shown in FIG. 2, a left hand has blood circulating from the leftventricle through the left subclavian artery 270 that supplies the leftarm. Because the left subclavian artery 270 is nearer a PDA 230 than thefurther upstream innominate artery 260, it may experience some mixing ofdeoxygenated blood and an alteration in flow due to the PDA 230.Duct-dependent CHD, therefore, may also be manifested as a reducedsaturation and an altered plethysmograph waveform measured at a lefthand tissue site as compared with the right hand baseline site, althoughto a lesser degree than with a foot site.

FIG. 3 illustrates a patient monitoring system 300, which provides bloodparameter measurements, such as arterial oxygen saturation, and whichcan be adapted as an advantageous diagnostic tool for duct-dependentCHD. The patient monitoring system 300 has a patient monitor 302 and asensor 306. The sensor 306 attaches to a tissue site and includes aplurality of emitters 322 capable of irradiating a tissue site 320 withdiffering wavelengths of light, such as the red and infrared wavelengthsutilized in pulse oximeters. The sensor 306 also includes one or moredetectors 324 capable of detecting the light after attenuation by thetissue 320. A sensor is disclosed in U.S. application Ser. No.11,367,013, filed on Mar. 1, 2006, titled Multiple Wavelength SensorEmitters, which is incorporated by reference herein. Sensors that attachto a tissue site and include light emitters capable of irradiating atissue site with at least red and infrared wavelengths are disclosed inone or more of U.S. Pat. Nos. 5,638,818, 5,782,757, 6,285,896,6,377,829, 6,760,607 6,934,570 6,985,764 and 7,027,849, incorporated byreference herein. Moreover, low noise optical sensors are available fromMasimo Corporation, Irvine, Calif.

As shown in FIG. 3, the patient monitor 302 communicates with the sensor306 to receive one or more intensity signals indicative of one or morephysiological parameters and displays the parameter values. Drivers 310convert digital control signals into analog drive signals capable ofdriving sensor emitters 322. A front-end 312 converts composite analogintensity signal(s) from light sensitive detector(s) 324 into digitaldata 342 input to the DSP 340. The DSP 340 may comprise a wide varietyof data and/or signal processors capable of executing programs fordetermining physiological parameters from input data. In an embodiment,the DSP executes the CHD screening and analysis processes described withrespect to FIGS. 7-9, below.

The instrument manager 360 may comprise one or more microcontrollerscontrolling system management, such as monitoring the activity of theDSP 340. The instrument manager 360 also has an input/output (I/O) port368 that provides a user and/or device interface for communicating withthe monitor 302. In an embodiment, the I/O port 368 provides thresholdsettings via a user keypad, network, computer or similar device, asdescribed below.

Also shown in FIG. 3 are one or more devices 380 including a display382, an audible indicator 384 and a user input 388. The display 382 iscapable of displaying indicia representative of calculated physiologicalparameters such as one or more of a pulse rate (PR), plethysmograph(pleth) morphology, perfusion index (PI), signal quality and values ofblood constituents in body tissue, including for example, oxygensaturation (SpO₂), carboxyhemoglobin (HbCO) and methemoglobin (HbMet).The monitor 302 may also be capable of storing or displaying historicalor trending data related to one or more of the measured parameters orcombinations of the measured parameters. The monitor 302 may alsoprovide a trigger for the audible indictor 384 for beeps, tones andalarms, for example. Displays 382 include for example readouts, coloredlights or graphics generated by LEDs, LCDs or CRTs to name a few.Audible indicators 384 include, for example, tones, beeps or alarmsgenerated by speakers or other audio transducers to name a few. The userinput device 388 may include, for example, a keypad, touch screen,pointing device, voice recognition device, or the like.

A patient monitor is disclosed in U.S. application Ser. No. 11,367,033,filed on Mar. 1, 2006, titled Noninvasive Multi-Parameter PatientMonitor, incorporated by reference herein. Pulse oximeters capable ofmeasuring physiological parameters including SpO₂, pleth, perfusionindex and signal quality are disclosed in one or more of U.S. Pat. Nos.6,770,028, 6,658,276, 6,157,850, 6,002,952, and 5,769,785, incorporatedby reference herein. Moreover, pulse oximeters capable of readingthrough motion induced noise are available from Masimo Corporation,Irvine, Calif.

A congential heart disease (CHD) monitor advantageously utilizes apatient monitor capable of providing multiple-site blood parametermeasurements, such as oxygen saturation, so as to detect, for example,hand-foot oxygen saturation differences associated with a PDA andrelated CHD.

One aspect of a CHD monitor is a sensor, a patient monitor and a DSP.The sensor is configured to emit optical radiation having a plurality ofwavelengths into a tissue site and to detect the optical radiation afterattenuation by pulsatile blood flowing within the tissue site. Themonitor is configured to drive the sensor, receive a sensor signalcorresponding to the detected optical radiation and to generate at leastone of a visual output and an audio output responsive to the sensorsignal. The DSP is a portion of the patient monitor and is programmed toderive a physiological parameter from sensor data responsive to thesensor signal. The physiological parameter is measured at a baselinetissue site and a comparison tissue site. The outputs indicate apotential CHD condition according to a difference between thephysiological parameter measured at the baseline tissue site and thephysiological parameter measured at the comparison tissue site.

Another aspect of a CHD monitor is a congenital heart disease screeningmethod providing a patient monitor and corresponding sensor. The sensoris capable of emitting optical radiation having a plurality ofwavelengths into a tissue site and detecting the optical radiation afterattenuation by pulsatile blood flowing within the tissue site. Thepatient monitor is capable of receiving a sensor signal corresponding tothe detected optical radiation and calculating a blood-relatedphysiological parameter. The physiological parameter is measured at abaseline tissue site and a comparison tissue site. The measuredphysiological parameter at the baseline tissue site and at thecomparison tissue site are compared. A potential CHD condition isindicated based upon the comparison.

A further aspect of a CHD monitor is a detection method determining aplurality of metrics responsive to sensor data derived from a pluralityof tissue sites on an infant, testing the metrics with respect topredetermined rules and thresholds, and outputting diagnosticsresponsive to the test results. The metrics are at least one of aphysiological parameter measurement, a cross-channel measurement and atrend. The diagnostics are responsive to the likelihood of congenitalheart disease.

Yet another aspect of a CHD monitor comprises a patient monitor, apre-processor means, an analyzer means and a post-processor means. Thepatient monitor is configured to receive sensor data from at least oneoptical sensor attached to a plurality of tissue sites on an infant. Thepre-processor means is for deriving at least one metric from the sensordata. The analyzer means is for testing the at least one metricaccording to at least one rule. The post-processor means is forgenerating diagnostics based upon results of the testing The at leastone rule defines when the at least one metric indicates a potential CHDcondition in the infant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a fetal heart depicting a ductusarteriosis;

FIG. 2 is an illustration of a neonatal heart depicting a patent ductusarteriosis (PDA);

FIG. 3 is a general block diagram of a patient monitoring system adaptedfor congenital heart disease (CHD) detection;

FIG. 4 is an illustration of a single patient monitor utilized for CHDdetection;

FIG. 5 is an illustration of multiple patient monitors utilized for CHDdetection;

FIG. 6 is an illustration of a single patient monitor and multi-sitesensor utilized for CHD detection;

FIGS. 7A-B is a flow diagram of a CHD screening embodiment;

FIG. 8 is a detailed block diagram of a CHD analyzer embodiment; and

FIG. 9 is a detailed block diagram of a preprocessor embodiment for aCHD analyzer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 4 illustrates CHD detection utilizing a single patient monitor 410and corresponding sensor 420. In general, the monitor 410 provides adisplay or other indicator that directs a caregiver or other user toattach the sensor 420 to an initial tissue site for a first measurementand then to one or more other tissue sites for additional measurements.This procedure is described in further detail with respect to FIGS.7A-B, below. For example, in a Phase I configuration 401, the sensor 420is attached to a neonate's right hand so that the monitor 410 generatesbaseline site measurements. In a Phase II configuration 402, the sensor420 is attached to a neonate's foot so that the monitor 410 generatescomparison site measurements. In an optional Phase III configuration403, the sensor 420 is attached to a neonate's left hand generatingmeasurements at an additional comparison site. During each phase401-403, the monitor 410 takes measurements for a length of timesufficient to determine user-selected parameters, which includes SpO₂and may include PR, PI, signal quality, pleth morphology, other bloodparameters such as HbCO and HbMET, and trends over a selected timeinterval for any or all of these parameters. In an embodiment, baselineright-hand measurements are made first, followed by measurements ateither foot, followed by optional left-hand measurements. In otherembodiments, the phase-order of measurements can be user-selected andcan be in any order and can include or exclude either the foot or theleft-hand measurements.

In an embodiment, a monitor-determined time or user-selectable timerdefines how long each site measurement is made, and a monitor displayand/or audible indicator signals the user when to switch sensor sites.In an embodiment, a user defines time intervals or times-of-day formaking repeat measurement cycles so as to obtain site difference trends.A monitor display and/or audible indicator signals the user when tobegin a measurement cycle.

FIG. 5 illustrates CHD detection utilizing multiple patient monitors510-520 and corresponding sensors 530-540. In an embodiment, a firstmonitor 510 and first sensor 530 provide measurements from a right-handtissue site. A second monitor 520 and second sensor 540 providemeasurements from a foot tissue site. An interface cable 550 or wirelesslink provides communications between the monitors 510-520. For example,the monitors 510-520 can communicate respective measurements via RS-232,USB, Firewire or any number of standard wired or wireless communicationlinks. In an embodiment, one monitor, such as the baseline right-handmonitor 510 acts as the master and the comparison (e.g. foot) monitor520 acts as a slave. The master monitor 510 generates the baselinemeasurements, transfers the comparison measurements from the slavemonitor 520, calculates the comparison parameters, such as oxygensaturation differences, displays the comparison parameters, calculatesalarm conditions based upon the measured and comparison parameters andgenerates alarms accordingly.

In other embodiments, the comparison site (e.g. foot or left-hand)monitor 520 is the master and the baseline (right-hand) monitor 510 isthe slave. In yet another embodiment, there are three networked monitorscorresponding to right-hand, left-hand and foot sites, with one monitoracting as a master and the other monitors acting as slaves. The mastermonitor, in this example, calculates oxygen saturation differences foreach pair of sites and generates alarms accordingly.

FIG. 6 illustrates CHD screening utilizing a single CHD patient monitor610 and a corresponding multi-site sensor 620. In an embodiment, themulti-site sensor 620 has two sensor heads 622-624 and a common sensorcable 628 for communication with the monitor 610. One sensor head 622 isattached to a baseline tissue site, e.g. a right-hand and another sensorhead 624 is attached to a comparison tissue site, e.g. either a foot ora left-hand. In another embodiment, a third sensor head 626 is availablefor attachment to a second comparison site, e.g. a left-hand. A multiplesite patient monitor is disclosed in U.S. Pat. No. 6,334,065 issued Dec.25, 2001 titled Stereo Pulse Oximeter which is assigned to MasimoCorporation, Irvine, Calif. and incorporated by reference herein.

FIGS. 7A-B illustrate a CHD screening process 700 corresponding to asingle monitor CHD detection embodiment, such as described with respectto FIG. 4, above. In general, the process 700 is described with respectto user actions 701 and monitor responses 702 and, likewise, monitorprompts 702 and user responses 701. In particular, once the monitorenters a CHD detection mode, the monitor prompts a user to attach thesensor successively to two or more tissue sites. In this manner, themonitor can compute baseline and comparison site measurements andcalculate site differences, such as in oxygen saturation, which tend topredict the likelihood or unlikelihood of CHD. In an embodiment, themonitor 702 communicates instructions to the user 701 or otherwiseprompts the user with display messages. Alternatively, or in addition todisplay messages, the monitor 702 can prompt the user via audio messagesor indicators, visual indicators such as panel lights or a combinationof the above. In an embodiment, the user 701 can trigger the monitor 702or otherwise respond to monitor 702 prompts via a panel-mounted pushbutton. Alternatively, or in addition to a push button, the user 701 cantrigger the monitor 702 or otherwise respond to the monitor 702 viatouch screen, touch pad, keyboard, mouse, pointer, voice recognitiontechnology or any similar mechanism used for accomplishing acomputer-human interface.

As shown in FIG. 7A, a user 701 initiates CHD screening 705 and themonitor 702 enters a CHD detection mode 710 in response. The monitor 702then prompts the user 701 to attach a sensor to a baseline site 715. Inresponse, the user 701 attaches a sensor to a first tissue site 720,such as a neonate's right hand, and pushes a button 725 to trigger themonitor to take baseline sensor measurements 730. The monitor 702displays the resulting baseline measurements 732 and prompts the user701 to reattach the sensor to a comparison site 735. In response, theuser 701 removes the sensor and reattaches it to a second tissue site740, such as either of a neonate's feet, and pushes a button 745 totrigger the monitor 702 to take comparison sensor measurements 750. Themonitor 702 displays the resulting comparison site measurements 755.

As shown in FIG. 7B, after taking baseline site and comparison sitemeasurements, the monitor 702 determines if a third site measurement isto be taken 760. If so, the monitor 702 prompts the user 701 to reattachthe sensor to an additional comparison site 765. In response, the user701 removes the sensor and reattaches it to a third tissue site 770,such as a neonate's left-hand, and pushes a button 775 to trigger themonitor 702 to take additional comparison site measurements 780. Themonitor 702 then displays the resulting measurements 785. The monitor702 determines if trend measurements are being made 787. If so, thenafter a predetermined delay the monitor 702 prompts the user tore-attach the sensor at the baseline site 715 (FIG. 7A) to begin anadditional series of measurements 730-785.

Also shown in FIG. 7B, after all site measurements are taken, themonitor 702 calculates the measurement differences between the baselineand comparison site(s) 790, calculates trends in measurements andmeasurement differences 790 and displays the results 792. The monitor702 then determines whether any site measurements, site measurementdifferences or trends are outside of preset limits 794. If limits areexceeded, the monitor generates visual and/or audio indicators of apotential CHD condition 796. For example, an audio alert or alarm of apotential CHD condition may be a low-level intermittent beep so as toindicate a diagnostic result and not be confused with other urgent carealarms. In one embodiment, if neonatal SpO₂ measurements from both aright hand and a foot are less than about 95% or a hand-foot differenceis greater than about ±3%, the monitor generates one or more indicatorsalerting a caregiver that a potential CHD condition exists.

FIG. 8 illustrates a CHD analyzer 800 that executes in the DSP 340 (FIG.3) and indicates a potential CHD or lack thereof. The CHD analyzer 800is advantageously responsive to multiple channels of sensor data 801 soas to generate CHD diagnostics 803. In an embodiment, the CHD analyzer800 executes the CHD screening process described with respect to FIGS.7A-B, above, receiving sensor data 342 (FIG. 3) derived from one tissuesite at a time. In another embodiment, the CHD analyzer 800 receivessensor data 342 (FIG. 3) derived from two or more sensor sites at atime, such as described with respect to FIGS. 5-6, above. The diagnosticoutput 803 can be used, for example, to generate displays or indicatorsuseful for grading a neonate with respect to a potential CHD conditionand the severity of that condition. In an embodiment, an instrumentmanager 360 (FIG. 3) convert CHD diagnostics 803 via a display driver362 (FIG. 3) and an audio driver 364 (FIG. 3) into one or more displays382 (FIG. 3) and audible indicators 384 (FIG. 3) for use by a physician,clinician, nurse or other caregiver.

In an embodiment, the CHD analyzer 800 has a pre-processor 900, a metricanalyzer 820, a post-processor 830 and a controller 840. Thepre-processor 900 has sensor data inputs 801 from one or more sensorchannels, such as described with respect to FIGS. 4-6, above. Thepre-processor 900 generates metrics 822 that may include, for example,physiological parameters, waveform features, and cross-channelcomparisons and trends, as described in further detail with respect toFIG. 9, below.

As shown in FIG. 8, the metric analyzer 820 is configured to testmetrics 822 and communicate the test results 824 to the post-processor830 based upon various rules applied to the metrics 822 in view ofvarious thresholds 826. As an example, the metric analyzer 820 maycommunicate to the post-processor 830 when a parameter measurementincreases faster than a predetermined rate, e.g. a trend metric exceedsa predetermined trend threshold.

Also shown in FIG. 8, the post processor 830 inputs test results 824 andgenerates CHD diagnostic outputs 803 based upon output definitions 832.For example, if the test result is that a trend metric exceeds a trendthreshold, then the output definition corresponding to that test resultmay be to trigger an audible alarm. Thresholds, rules, tests andcorresponding outputs are described in further detail with respect toTABLE 1, below.

Further shown in FIG. 8, the controller 840 has an externalcommunications port 805 that provides predetermined thresholds, whichthe controller 840 transmits to the metric analyzer 820. The controller840 may also provide metric definitions 824 to the pre-processor 900 anddefine outputs 832 for the post-processor 830.

In an embodiment, CHD screening grades a neonate with respect to alikelihood of a CHD condition utilizing green, yellow and redindicators. For example, a green panel light signals that no metricindicates a potential CHD condition exists. A yellow panel light signalsthat one metric indicates a potential CHD condition exists. A red panellight signals that more than one metric indicates that a potential CHDcondition exists. In an embodiment, the CHD analyzer 800 provides adiagnostic output 803 according to TABLE 1, below. The terms Sat_(xy),ΔSat_(xy) and Δt listed in TABLE 1 are described with respect to FIG. 9,below. Various other indicators, alarms, controls and diagnostics inresponse to various combinations of parameters and thresholds can besubstituted for, or added to, the rule-based outputs illustrated inTABLE 1.

TABLE 1 CHD Analyzer Rules and Outputs RULE OUTPUT If Sat > Sat limitthreshold (all channels); Then illuminate green Sat_(xy) < Sat_(xy)limit threshold (all indicator. cross-channels); and ΔSat_(xy)/Δt <Sat_(xy) trend threshold (all cross-channels). If Sat < Sat limitthreshold (any channel); Then illuminate Sat_(xy) > Sat_(xy) limitthreshold (any yellow indicator cross-channel); or ΔSat_(xy)/Δt >Sat_(xy) trend threshold (any cross-channel). If Sat < Sat limitthreshold (any channel); and Then illuminate red Sat_(xy) > Sat_(xy)limit threshold (any indicator cross-channel). If Sat < Sat limitthreshold (any channel); and Then illuminate red ΔSat_(xy)/Δt > Sat_(xy)trend threshold (any indicator cross-channel).

FIG. 9 illustrates a preprocessor embodiment 900 that inputs sensor data801 derived from one or more tissue sites and outputs metrics 822. Thepreprocessor 900 has a parameter calculator 910, a waveform processor920, a cross-channel calculator 930 and a trending function 940. Theparameter calculator 910 outputs one or more physiological parametersderived from pulsatile blood flow at a tissue site. These parameters mayinclude, as examples, arterial oxygen saturation (SpaO₂), venous oxygensaturation (SpvO₂), PR and PI to name a few. In an embodiment, theparameter calculator 910 generates one or more of these parameters foreach sensor data channel. The waveform processor 920 extracts variousplethysmograph features for each data channel. These features mayinclude, for example, the area under the peripheral flow curve, theslope of the inflow phase, the slope of the outflow phase, the value ofthe end diastolic baseline and the size and location of the dicroticnotch. The cross-channel calculator 930 generates cross-channel values,such as Sxy=SpO₂ (baseline site)−SpO₂ (comparison site). In anembodiment, the calculator 930 can also generate same-channel values,such as SpaO₂−SpvO₂ from the same sensor site. The trending function 940calculates trends from the parameter calculator 910, the waveformprocessor 920 or the cross-channel calculator 930. The trending function940 stores historical values and compares these with present values.This comparison may include Δp/Δt, the change in a parameter over aspecified time interval, which may also be expressed as a percentagechange over that interval. An example is ΔSat_(xy)/Δ_(t), the change inthe oxygen saturation difference between two tissue sites over aspecified time interval.

Although described above with respect to optical sensor inputsresponsive to pulsatile blood flow, in an embodiment, the CHD monitormay include sensor inputs and corresponding algorithms and processes forother parameters such as ECG, EEG, ETCO₂, respiration rate andtemperature to name a few. Although a CHD analyzer is described above asa program executed by a patient monitor DSP, the CHD analyzer can be, inwhole or in part, hardware, firmware or software or a combinationfunctioning in conjunction with or separate from the DSP. Further, theCHD analyzer can be configured, in whole or in part, as logic circuits,gate arrays, neural networks or an expert system, as examples. In anembodiment, a CHD monitor, such as described above, for example, asincorporating a patient monitor, CHD analyzer and corresponding CHDscreening process, is marketed with instructions on grading a neonate,infant or patient with respect to the likelihood of a CHD condition.

A congential heart disease monitor has been disclosed in detail inconnection with various embodiments. These embodiments are disclosed byway of examples only and are not to limit the scope of the presentinvention, which is defined by the claims that follow. One of ordinaryskill in the art will appreciate many variations and modification.

What is claimed is:
 1. A congenital heart disease monitor comprising: adisplay; a sensor configured to emit optical radiation having aplurality of wavelengths into a tissue site and to detect the opticalradiation after attenuation by pulsatile blood flowing within the tissuesite; a patient monitor configured to drive the sensor, receive a sensorsignal corresponding to the detected optical radiation and to generateat least one of a visual output and an audio output responsive to thesensor signal; one or more hardware processors within the patientmonitor programmed to derive a physiological parameter measurementcomprising oxygen saturation from sensor data responsive to the sensorsignal and determine an indication of a congenital heart diseasecondition for output to the display, the one or more hardware processorsfurther configured to: electronically determine a first oxygensaturation from a first channel corresponding to a first measurementsite; electronically determine a second oxygen saturation from a secondchannel at a second measurement site; electronically determine adifference of oxygen saturation between the first channel and the secondchannel; electronically determine a rate of change of the difference ofoxygen saturation over time between the first channel and the secondchannel; and electronically determine a first metric based on acomparison of the first oxygen saturation corresponding to the firstchannel with a saturation limit threshold; electronically determine asecond metric based on a comparison of the second oxygen saturationcorresponding to the second channel with the saturation limit threshold;electronically determine a third metric based on a comparison of thedifference of oxygen saturation with a cross channel saturation limitthreshold; electronically determine a fourth metric based on acomparison of the rate of change of the difference of oxygen saturationover time between the first channel and the second channel with a crosschannel saturation trend threshold; electronically generate a firstindicator based on the following electronic determinations: the firstmetric indicating that the first oxygen saturation is greater than thesaturation limit threshold, the second metric indicating that the secondoxygen saturation is greater than the saturation limit threshold, thethird metric indicating that the difference of oxygen saturation is lessthan the cross channel saturation limit threshold, and the fourth metricindicating that the comparison of the rate of change of the differenceis less than the cross channel saturation threshold; and electronicallygenerate a second indicator based on the following electronicdeterminations: the first metric indicating that the first oxygensaturation is greater than the saturation limit threshold or the secondmetric indicating that the second oxygen saturation is greater than thesaturation limit threshold, the first indicator corresponding to a lowerrisk of congenital heart disease than the second indicator.
 2. Thecongenital heart disease monitor of claim 1, wherein the first indicatorcomprises a first color and the second indicator comprises a secondcolor different from the first color.
 3. The congenital heart diseasemonitor of claim 1, wherein the rate of change of the difference overtime comprises a percentage change over a time interval.
 4. Thecongenital heart disease monitor of claim 1, wherein the one or morehardware processors is further configured to determine that trend datais acquired and generate an indicator to change location of the sensorafter determining that the trend data is acquired.
 5. The congenitalheart disease monitor of claim 1, wherein the first indicator or thesecond indicator comprises an audio alarm.
 6. A congenital heart diseasescreening method comprising the steps of: electronically measuring,using a sensor and a patient monitor, a first oxygen saturation at afirst patient site; electronically measuring, using the sensor and thepatient monitor, a second oxygen saturation at the second patient site;electronically determining a difference between the first oxygensaturation and the second oxygen saturation; electronically determininga rate of change of the difference over time; electronically determininga first metric based on a comparison of the first oxygen saturation witha saturation limit threshold; electronically determining a second metricbased on a comparison of the second oxygen saturation with thesaturation limit threshold; electronically determining a third metricbased on a comparison of the difference with a cross channel saturationlimit threshold; electronically determining a fourth metric based on acomparison of the rate of change of the difference over time with across channel saturation trend threshold; electronically generating afirst indicator based on the following electronic determinations: thefirst metric indicating that the first oxygen saturation is greater thanthe saturation limit threshold, the second metric indicating that thesecond oxygen saturation is greater than the saturation limit threshold,the third metric indicating that the difference of oxygen saturation isless than the cross channel saturation limit threshold, and the fourthmetric indicating that the comparison of the rate of change of thedifference is less than the cross channel saturation threshold; andelectronically generating a second indicator based on the followingelectronic determinations: the first metric indicating that the firstoxygen saturation is greater than the saturation limit threshold or thesecond metric indicating that the second oxygen saturation is greaterthan the saturation limit threshold, the first indicator correspondingto a lower risk of congenital heart disease than the second indicator;and displaying the generated first indicator or the second indicator ona display screen.
 7. The congenital heart disease screening methodaccording to claim 6, comprising the further step of prompting thesuccessive attachment of the sensor to the first site and the secondsite.
 8. The congenital heart disease screening method of claim 6,wherein the first indicator comprises a first color and the secondindicator comprises a second color different from the first color. 9.The congenital heart disease screening method of claim 6, wherein therate of change of the difference over time comprises a percentage changeover a time interval.
 10. The congenital heart disease screening methodof claim 6, further comprising determining that trend data is acquiredand generating an indicator to change location of the sensor afterdetermining that the trend data is acquired.
 11. The congenital heartdisease screening method of claim 6, wherein the first indicator or thesecond indicator comprises an audio alarm.